Most heating and air conditioning systems employ one of two types of air diffusers, namely, fixed-opening air diffusers and variable-opening air diffusers. The variable-opening air diffusers are constructed in a manner which allows the volume of air discharged into the space to be heated or cooled to be varied or modulated. Thus, such diffusers are known as variable air volume or VAV diffusers.
Additionally, there are numerous types of controllers for VAV diffuser systems, including pneumatic, electrical and thermal sensor-actuator systems. Depending upon the controller, the movable vanes or elements varying air flow can be driven and controlled at each diffuser or at groups of diffusers.
VAV diffusers have the advantage over fixed-opening diffusers of greater control so that the heating and cooling can be better tailored to the demands of the various parts of a building in which the system is installed. Sun-facing rooms need more air conditioning in the summer and less heating in the winter. The heating and cooling requirements, moreover, change during the day as environmental conditions change surrounding the structure. VAV systems, therefore, tend to be more energy-efficient and provide more comfort control zones than fixed-opening systems.
Although not always the case, fixed-opening air diffusers often have lower initial cost than VAV diffuser systems. Accordingly, there are many older buildings, particularly older office buildings, that have fixed-opening diffuser heating and air conditioning systems. As energy-awareness has increased, it has become apparent that fixed-opening systems are energy inefficient and do not provide the required control features that a VAV diffuser system could provide. Many of these older office buildings, however, also have made wide-spread use of asbestos. Thus, the steel framework of older buildings often has a layer of asbestos over the steel to protect the framework from melt-down in a fire. Similarly, the original air conditioning duct work in older buildings may include asbestos flocking or tape as an insulator.
Broadly, it is well-known in the heating and air conditioning industry to change fixed-opening air diffusers to VAV air diffusers. This has been done by disconnecting the complete diffuser and replacing it with a new VAV diffuser. In electrical and pneumatic conversions, the necessary electrical or pneumatic wires and conduit also must be added to control diffuser operation. In drop-ceiling buildings, in which the air diffusers are mounted to a T-shaped support grid for the ceiling tiles, however, opening up the ceiling to replace an air diffuser can be relatively easily done, but it is very hazardous. While the ceiling tiles lift out of the grid rather easily, the top surfaces of the tiles and of the air diffuser housings can be covered with asbestos dust.
Accordingly, many old heating and cooling systems which employ fixed-opening air diffusers are candidates for conversion to VAV air diffuser systems, but the asbestos hazard makes such conversion dangerous and prohibitively expensive. Conversions in such buildings may require workers to wear protective clothing and use breathing apparatus, as well as require that the area be sealed during the replacement process. There are, therefore, many energy inefficient office buildings using fixed-opening air diffusers whose owners essentially cannot afford to convert to more efficient and comfortable heating and cooling systems.
Accordingly, it is an object of the present invention to provide a method and apparatus for converting fixed-opening air diffusers to individually-controlled VAV air diffusers substantially without disturbing the structure in which the fixed-opening air diffuser is mounted.
A further object of the present invention is to provide a method and apparatus for converting fixed-opening air diffusers to VAV air-diffusers which minimizes the exposure to dangerous or hazardous materials.
Another object of the present invention is to provide a method and apparatus for installing a variable air volume, individually-controlled air diffuser in a structure which possibly could have dangerous or hazardous materials in it without need for specially trained personnel and protective equipment.
The apparatus and method of the present invention have other objects and features of advantage which will become apparent from, or are set forth in more detail in, the following description of the Best Mode of Carrying Out the Invention and the accompanying drawing.